GAITHERSBURG, Md., August 23, 2007 /PRNewswire/ -- MedImmune,
Inc. today announced that in a Phase 3 study, motavizumab was shown
to reduce hospitalizations due to respiratory syncytial virus (RSV)
by 83 percent as compared to placebo (8.3 percent in placebo arm
vs. 1.4 percent in motavizumab; p<0.001), as the trial's primary
endpoint. In addition, the trial showed a 71-percent reduction in
the incidence of RSV-specific lower respiratory infections (LRIs)
requiring outpatient management (9.5 percent in placebo group and
2.8 percent in the motavizumab group; p<0.001), which was a
secondary endpoint.

Motavizumab is an investigational monoclonal antibody (MAb)
being evaluated for its potential to prevent serious disease caused
by RSV in high-risk pediatric patients. This Phase 3 trial involved
1,410 full-term infants less than six months of age in two Native
American populations. In previous medical studies these populations
were shown to have high rates of hospitalization due to RSV.

The randomized (2:1), double-blind study was designed to compare
monthly intramuscular injections of motavizumab against placebo.
After an interim analysis conducted by an independent data safety
monitoring committee, the study was unblinded early due to
statistical evidence demonstrating that motavizumab reduced RSV
hospitalizations and LRIs requiring outpatient medical management
within this population. Kate O'Brien, M.D., associate professor at
the Center for American Indian Health, Johns Hopkins Bloomberg
School of Public Health, served as the study's principal
investigator.

"We are pleased with the results of this study which support the
positive results seen in our Phase 3 pivotal trial comparing
motavizumab and Synagis(R) (palivizumab) that were previously
reported at the Pediatric Academic Societies meeting in May 2007,"
said Genevieve Losonsky, M.D., vice president, clinical
development, infectious disease, MedImmune.

Motavizumab was well tolerated in these Native American infants,
with an overall incidence and severity of adverse events (AEs) that
were similar between the motavizumab and the placebo groups. The
mortality rates were not statistically different between groups
(0.4 percent in the placebo arm, n=2 and 0.3 percent in the
motavizumab arm, n=3) and were not considered to be related to the
study drug. As was suggested in the pivotal Phase 3 trial conducted
in high-risk, preterm infants, rates of hypersensitivity related
skin rashes within two days of dosing were seen in about one
percent of treated children in the motavizumab group.

MedImmune's Commitment to RSV Prevention

MedImmune is a world leader in the development of innovative
therapeutic biologic products to prevent RSV disease. In 1996,
MedImmune launched the first anti-RSV drug, RespiGam(R)
(respiratory syncytial virus immune globulin intravenous (human)
(RSV-IGIV)), which was a polyclonal antibody administered via
four-hour intravenous infusion. In 1998, MedImmune introduced
Synagis, which was a significant product improvement as a monthly
intramuscular injection for the prevention of severe RSV, as well
as being the first MAb to receive U.S. Food and Drug Administration
(FDA) approval for an infectious disease. With the development of
motavizumab, MedImmune continues to reinforce its commitment to
developing anti-RSV products. In a head-to-head comparative Phase 3
trial with Synagis, motavizumab met its primary endpoint of
reducing RSV-related hospitalizations in high-risk pediatric
patients and met its secondary endpoint of reducing medically
attended, outpatient respiratory tract infections in that patient
group. MedImmune is also developing a small-molecule product
candidate to prevent RSV as well as a vaccine against RSV, both of
which are in Phase 1 clinical trials.

About RSV

Each year, up to 125,000 infants in the U.S. are hospitalized
with severe RSV infections, the leading cause of lower respiratory
tract infections in infants in the United States. RSV is the most
common respiratory infection in infancy or childhood. Approximately
one-half of all infants are infected with RSV during the first year
of life, and nearly all children have been infected at least once
by the time they reach their second birthday. Children born
prematurely as well as those with chronic lung disease (CLD) or
congenital heart disease (CHD) are at highest risk for severe
disease and hospitalization due to RSV. The virus may also cause
severe illness in other high-risk groups such as the elderly, those
with underlying respiratory or cardiac disease, and those with
compromised immune systems (e.g., bone marrow transplant
patients).

About Motavizumab

Motavizumab, formerly known as Numax(R), is an investigational
humanized MAb being evaluated for its potential to prevent serious
lower respiratory tract disease caused by RSV in pediatric patients
at high risk of RSV disease. Phase 1 and Phase 2 study data have
been reported showing that motavizumab appears to have a similar
safety and pharmacokinetic profile to Synagis in infants.
Additionally, in early phase studies children treated with
motavizumab had reduced RSV replication in the upper respiratory
tract. In its first pivotal trial, which was a head-to-head
comparative trial with Synagis, motavizumab demonstrated a
26-percent reduction in RSV hospitalizations due to RSV and a
50-percent reduction in the incidence of RSV lower respiratory
tract infections requiring outpatient management, its secondary
endpoint.

About Synagis

Synagis is the only monoclonal antibody approved by the FDA to
help prevent an infectious disease. Synagis was approved for use in
the United States in 1998, Europe in 1999, and Japan in 2002.
Synagis is currently available in 62 countries.

Synagis is indicated for the prevention of serious lower
respiratory tract disease caused by respiratory syncytial virus
(RSV) in pediatric patients at high risk of RSV disease and is
administered by intramuscular injection. The safety and efficacy of
Synagis were established in infants with bronchopulmonary dysplasia
(BPD), infants with a history of prematurity (less than or equal to
35 weeks gestational age), and children with hemodynamically
significant congenital heart disease. The first dose of Synagis
should be administered prior to commencement of the RSV season,
which usually starts in the fall and runs through the spring.
Patients, including those who develop an RSV infection, should
continue to receive monthly doses throughout the season.

Very rare cases (<1 per 100,000 patients) of anaphylaxis and
rare (<1 per 1,000 patients) hypersensitivity reactions have
been reported with Synagis. Cases of anaphylaxis were reported
following re-exposure to Synagis and rare severe hypersensitivity
reactions occurred on initial exposure or re-exposure. If a severe
hypersensitivity reaction occurs, therapy with Synagis should be
permanently discontinued. If milder hypersensitivity reaction
occurs, caution should be used on re-administration of Synagis.

In clinical trials, the most common adverse events occurring at
least one percent more frequently in Synagis-treated patients than
controls were upper respiratory infection, otitis media, fever and
rhinitis. Cyanosis and arrhythmia were seen in children with
CHD.

The pivotal trial for Synagis was called the IMpact trial and
comprised a total of 1,502 children who were randomized (500
placebo, 1,002 Synagis) in a double-blind, placebo-controlled
protocol where 1,486 children completed the study's follow-up.

In the IMpact trial, monthly prophylaxis with Synagis via
intramuscular injections was associated with a 55-percent reduction
in hospitalization as a result of RSV (p=<0.001). Reductions
were observed in both children with bronchopulmonary dysplasia (38
percent reduction) and premature children without BPD (78 percent
reduction). Approximately 50 percent of the children in the
analysis had BPD.

Outside the United States, Synagis is distributed by
Illinois-based Abbott, a global, broad-based health care company.
Abbott also has the ex-U.S. distribution rights to motavizumab.

About MedImmune, Inc.

MedImmune strives to provide better medicines to patients, new
medical options for physicians and rewarding careers to employees.
Dedicated to advancing science and medicine to help people live
better lives, the company is focused on the areas of infectious
diseases, cancer and inflammatory diseases. With approximately
3,000 employees worldwide and headquarters in Maryland, MedImmune
is wholly owned by AstraZeneca plc . For more information, visit
MedImmune's website at http://www.medimmune.com.